Best thing for inexpensive would be to download the Restoration Specialties
http://www.restorationspecialties.com/ catalog. They have an assortment of most of the channels still available today with details and cross section illustrations. You can see what they have in the style closest to yours and order bulk. Not that difficult to bend and cut them. There might be a bit of work mounting them since a lot of the original pieces were riveted. Pop rivets are a bit large but there are ways they can be done -- sometimes using small screws.
For considerably more money, Steele, Kanter and maybe others have some precut, premade kits for some models but, as I recall you still have to figure out mounting on some items.
As to the moving back and forth part, the very bottom of the rear channel has a bracket which bolts to door and attaches to channel to provide adjustment. Point being that bracket becoming disconnected from channel either from rusting or bolt or rivet falling out and letting the window move was an issue for some. Don't remember the front channel arrangement exactly but check it as well.
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